For majors in Earth & Environmental Sciences, I teach Mineralogy (EES 12), Analytical
Methods in the Earth Sciences (EES 100), and Igneous and Metamorphic Petrology (EES
101). At the graduate level, I teach Volcanology (EES 271) and various versions of
Magmatism and Tectonics of the Western U.S. (EES 250T). In 250T, we usually investigate
problems of magmatism and/or tectonics that can at least be partially tested by the
examination of field data. Each such trip then, involves a 5-day to 1-week field trip,
usually to the western Basin and Range, the Grand Canyon region, or the lower Colorado
River (between AZ and CA). Research is a key component to an Earth Science education
and so students in my classes conduct research projects, which involve field and laboratory
experiences. Our X-ray fluorescence (XRF) and X-ray diffraction (XRD) instruments
are utilized as lab components in these courses. For non-majors, I teach Environmental
Earth and Life Science (NSCI 115). A goal in this course is to illustrate how a scientific
understanding of our planet is crucial to many aspects of our daily lives.

Research Activities in Mineralogy and Igneous Petrology

My research interests are several. I am interested in how the internal engine of
our planet works. My research group thus attempts to estimate the depths and pressures
of partial melting in Earth’s mantle, to better understand mantle circulation. The
questions I am attempting to answer are: How hot are mantle plumes, and at what depth
does melting begin? How can plumes be identified? What is the composition of Earth’s
mantle, and do mantle plumes sample a distinct mantle source? I am also interested
in understating how volcanoes work. On this topic, my students and I investigate the
ascent and transport of magma through the crust and uppermost mantle, and attempt
to determine the various controls on magma transport and eruption. The relevant questions
here are: How deeply rooted are magma plumbing systems, and at what depths are magmas
stored prior to eruption? Do such storage depths change over time, or vary with tectonic
environment? What are the controls on the transport of magma through the crust? Finally,
I have recently begun investing plutons in the western Sierra Nevada. In this part
of the range, it is possible to see deep-level exposures, which provide insights as
to how structurally high levels of plutons (the granitoids, that comprise the bedrock
of most of the range) are developed? Key questions here are: What are the compositions
of primitive magmas that give rise to granitoid batholiths? Which processes are most
important for deriving granitic magmas: crustal partial melting, or differentiation.
Can mafic enclaves provide clues regarding the differentiation and magma mixing processes
that generate batholiths?

Presently, several students are working, in collaboration with Michael Clynne of
the U.S.G.S., at the Lassen Volcanic Center in northern California, in particular
at Lassen Peak and Chaos Crags. Some students are also investigating “ancestral” Cascade
volcanism, in the central Sierra Nevada, in collaboration with Cathy Busby, at UC
Santa Barbara. Several students of mine are also working in collaboration with Scott
Paterson at USC, to understand various Sierran granitic plutons, and the Guadalupe
Igneous Complex (in the Sierra foothills, below Mariposa) in particular. Finally,
I have some new collaborators in Pisa (Pietro Armienti) and Rome (Silvio Mollo). Pietro
and I are investigating means to estimate deep-level ascent rates of magmas, while
Silvio and I are using his experimental results to better understand mineral growth
rates and kinetics.

Downloads

I have put together several spreadsheets that can be used to calculate the P-T conditions
of crystallization or partial melting, and mantle potential temperatures.

The spreadsheets Clinopyroxene and Orthopyroxene respectively calculate the P-T conditions
for clinopyroxene-liquid and orthopyroxene-liquid equilibrium. The spreadsheet Feldspar-liquid
calculates T and water contents for plagioclase-saturated liquids, and T for alkali
feldspar-saturated liquids. The workbook Olivine and glass calculates the T of olivine-liquid
equilibrium and the T for silicate liquid (glass) given only the composition of the
liquid itself. This workbook also allows for the calculation of T using the graphical
approach of Roeder and Emslie (1970) approach (see Putirka, 2005). The spreadsheets
Two-feldspar and Two pyroxene respectively calculate the T of equilibration for equilibrium
pairs of alkali and plagioclase feldspar and equilibrium pairs of ortho- and clino-pyroxene
(no liquid composition required for input). The spreadsheet Silica activity calculates
the equilibrium pressure for silicate liquids in equilibrium with olivine and orthopyroxene;
T is required as input, which is best derived from one of the models presented in
the Olivine and glass spreadsheet. The workbook Mantle Potential Temperatures allows
for the calculation of mantle potential temperature, given a primitive liquid and
olivine composition; P and T are calculated from olivine thermometry and Si activity,
but can also be entered directly. In the same workbook, a separate spreadsheet allows
for the calculation of mantle potential temperature if an olivine-liquid temperature
and equilibration depth are known. Other parameters, like the heat of fusion or adiabatic
gradient, can be easily changed. This workbook also contains a spreadsheet that allows
one to calculate the composition of a liquid in equilibrium with mantle olivine (to
use as input to obtain mantle pot. T) using a primitive olivine-saturated liquid as
input; other required inputs are the Fo content of mantle olivine, and the Fo content
of the olivine to be added or subtracted from the given liquid. This spreadsheet can
only be used for putative liquids that are thought to be saturated with olivine only,
and so lie on what is called an “olivine control line”.

Laboratory Facilities

We have a PANalytical X’Pert Pro powder X-ray Diffractometer with an X’Celerator detector (acquired in 2005). This instrument plays an important role in the projects described
below.